The present invention relates to a prism-shaped intermittently-rotating device for supporting, in equidistant positions, a plurality of lower half-molds of the type used in automatic sand core molding machines in order to allow, with a single upper half-mold, to expel one or more finished cores simultaneously with the molding of another core.
As is known, sand core molding machines use openable molds, i.e. molds constituted by two half-molds arranged opposite to each other in a vertical direction and mounted on supports so that they can be closed by mating, in such a manner that they can be filled with sand, which is injected under pressure through an injection head, and are subsequently opened, normally by spacing one of said half-molds with respect to the other one, in order to allow extraction of the molded core.
The lower half-molds are generally supported by a box-like containment body, commonly termed "core box", which is supported by a quadrangular plate and is removably anchored thereto: said plate has, in its peripheral region, a raised border which has a quadrangular cross-section, so as to form a flat frame for the support and anchoring of the core box; said frame is essentially formed by supporting plates which have a limited width.
In all sand core molding machines that use an upper half-mold movable toward and away from the corresponding half-mold which is mounted in fixed position on the core box, after molding and consequent degassing in a known manner, the upper half-mold is raised, whereas the core, formed in the lower fixed half-mold and partially protruding from the edge of said half-mold, is raised and extracted from the half-mold by means of extractor pins which are carried by two extraction plates actuated in a vertical direction by a hydraulic cylinder. The core is then gripped by clamps or the like and then moved laterally and immersed in a deburring tank or in other devices capable of eliminating burr. The core, thus cleaned, is then removed on trolleys or the like.
In practice, this method of operation entails considerable downtimes between one molding operation and the next. This is due to the need to extract the core when the machine is not moving and to remove said core from the fixed half-mold, and is also due to the time required to close the upper half-mold on the lower half-mold before performing the subsequent injection of the molding sand. Furthermore, the finished core must be extracted with particular care, and its removal requires particular grip means which are rather slow in their intervention and movement.
Due to all these reasons, productivity is limited and production costs are rather high, especially for the production of a limited number of cores using the same metal "pattern" in the lower half-mold.